Hi, Lois. I think it might help you to remember that the Divergent Meridians move energy between the Wei and the Yuan levels, which is so unique. That is why you use the needle technique that moves energy from Yuan to Wei, or from Wei to Yuan, that three-level needling that you were describing (deep-superficial-deep, or superficial-deep-superficial).
On the other hand, the Eight Extra meridians only work with energy in the Yuan level, so there is no three-level needling, you simply vibrate with the energy of the Yuan energies, which hooks you up to the entire Quantum Field and makes everything possible. I do a LOT of eight extras for this reason: I love hooking people up to the field of all possibilities!
I hope this helps explain why Divergent needling techniques don’t apply to Eight Extra meridians. (If I’m over-explaining, I apologize.)